As for conventional blocks for pavement, there are general pavement blocks prepared by mixing aggregates such as rubble, sand and cement in appropriate portions, casting the mixture into a mold, and curing; and rubber blocks prepared by mixing waste-tire chips and/or waste-rubber chips with adhesives and pigments, and molding in a predetermined block shape.
However, these conventional blocks for pavement were not permeable. Thus, in case of heavy rain, except for only some part of the rain permeating through crevices among blocks, most of the rain did not sink into the ground, but flowed through roadside drainage system to river, stream, waste-water treatment plant or public water area. Therefore, in case of a localized torrential downpour for a short period of time or a heavy rain for a long period of time during the rainy season, the drained rain and water may overflow the river and stream, causing very dangerous and unstable situation. Also, as the rain and water could not permeate into the conventional pavement blocks, it obstructed safe passage and caused a lot of inconvenience to pedestrians.
In order to overcome such disadvantages of the conventional pavement blocks, permeable and drainage pavement blocks have been developed, among which Korean Utility Model Registration No. 195525 registered on Jun. 29, 2000 entitled “permeable blocks” discloses blocks for pavement or driveway. In this utility model, in order to facilitate the permeation of rain or water, each of the blocks includes grooves on side and top surfaces thereof to perforate through the top surface and the bottom surface of the block.
Further, Korean Utility Model Registration No. 248505 registered on Sep. 17, 2001 entitled “pavement blocks with draining function” discloses drainage pavement blocks used for parking lots or sidewalks, each of which includes a central hollow space and overflows in the center of the top and side surfaces thereof, and each of which is filled with permeable concrete in the central hollow space and the overflows.
Meanwhile, in order to overcome disadvantages of conventional impermeable pavement blocks, to prevent earth and sand's washing away from a slope of a dike, and to secure underground water resources by inducing rain or water to the ground, Korean Patent No. 165047 patented on Sep. 15, 1998 discloses permeable pavement blocks, which have the permeability coefficient of 10×10−4 cm/sec and the porosity of 5–10% and comprise 102 parts by weight of water, 410 parts by weight of cement, 100 parts by weight of sand, 1685 parts by weight of short particle aggregates (5–10 mm diameter), 1.8 parts by weight of a retardant, and 1.0 part by weight of resin.
In addition, Korean Utility Model Registration No. 289645 registered on Sep. 4, 2002 discloses “permeable concrete blocks with a waste-tire chip layer”, comprising a lower permeable-concrete layer prepared by mixing aggregates having the size of 13 mm or less, cement, water and admixture products in predetermined ratios; and an upper waste-tire chip layer provided in the thickness of 10–20 mm by mixing 100 g of waste-tire chips of 13 mm or less, 7–21 g of a binder, and 1–5 g of an inorganic pigment.
The permeable concrete blocks as disclosed in the above utility model had bi-directional permeability allowing rain or water to penetrate into the ground and to evaporate into the earth's surface, so that trees and plants could be provided with life-giving water and flooding of the river could be prevented. Also, by using recycled waste tires which have been one of the environmental pollutants, the blocks did not only absorb impact on foot, but also contributed to the protection of environment and mobility of old and feeble people.
However, since the waste tire's smell of rubber lasted for a long time, the blocks using the waste tire could not provide a pleasant sense of smell. Further, since the urethane, epoxy and acrylic resin binders used to adhere the waste-tire chips were those available in the market, there have been demands for a binder which enhances the adhesive strength and maintains the strength and durability of the blocks for a long time.
Further, conventional pavement blocks using waste-tire chips or rubber had disadvantages in that, upon exposure to the high temperature heat of the sun rays during summer, the surface temperature of the blocks abruptly increases and the elastic waste-tire chip layer is separated from or comes off the lower supporting layer. Also, during the pavement construction, it was inconvenient to fill the space formed between neighboring permeable blocks with sand and the like.
Accordingly, the inventor of the present invention studied and researched into materials and binders for the permeable pavement blocks, and as a result, the inventor completed the present invention by using waste-polyurethane chips in place of waste-tire chips as a main component of the permeable elastic pavement blocks and developed a binder to secure the binding between an upper polyurethane-chip layer and a lower permeable-concrete layer as well as the binding among the waste-polyurethane chips.